The Manitoba government will close Gimli, Winnipeg Beach, Balsam Bay and Arness harbours this spring to stop an infestation of zebra mussels.
Conservation Minister Gord Mackintosh says the government will spend $500,000 to spread potash to control and perhaps even eradicate the mussels.
He says it will likely take about two weeks in late May or early June.
The minister says officials are looking at a staging process to ensure those who fish can still access the lake when the season starts.
Mackintosh says this is the first time in the world a potash application has been applied to an open waterway.
The government is taking the action on the advice of a science advisory committee that was put together when zebra mussels were discovered in Lake Winnipeg last fall.
Zebra mussels are an invasive aquatic species that can disrupt the food chain and clog water pipes. They have already caused damage in the Great Lakes and spread in 2010 to North Dakota.
The mussels multiply rapidly, gobble up plankton and help create algae. Zebra mussels also attach themselves to solid objects, clogging municipal and residential water supply pipes and more. They spread by attaching themselves to boats.
Manitoba has been trying to stop the arrival of zebra mussels for years by urging boat owners to inspect and clean their vessels before bringing them from other jurisdictions.